Microbial Metabolism & Gene Regulation

Question 1

Photorhabdus luminescens has a complex life cycle that requires two different phenotypes. Why might another bacterium need to regulate gene expression?
Choose all correct answers.
A An E. coli bacterium might be moved from a medium with lactose to a medium with glucose and lactose.
B An E. coli bacterium may move from an environment with neutral pH to an environment with a slightly acidic pH.
C An E. coli bacterium consumes lactose at a consistent rate in a medium with abundant lactose and without having alternate carbohydrate sources added.
D An E. coli bacterium may have an excess of tryptophan and have no need for additional tryptophan.

Answer 1

A
B
D

Question 2

The introductory passage cites a research paper titled, “A single promoter inversion switches Photorhabdus between pathogenic and mutualistic states.” From this title, and from the information in the chapter, what do you know about the genetic changes involved in the switch?
Choose the best answer.
A A single piece of DNA where DNA polymerase binds to initiate transcription is reversed.
B A single piece of DNA where RNA polymerase binds to initiate translation is reversed.
C A single sequence of DNA containing structural genes is reversed.
D A single piece of DNA where RNA polymerase binds to initiate transcription is reversed.

Answer 2

D

Question 3

The introduction states that “Using fluorescent gene reporters, microbiologists have been able to visualize this elegant switch in a pure culture of Photorhabdus.” Which of the following examples describes a fluorescent gene reporter?
Choose the best answer.
A It is a gene that produces a protein that fluoresces in response to markers on a host/insect cell, indicating that the bacterium has switched from the mutualistic to the pathogenic state.
B It is a gene that fluoresces in a way that allows researchers to easily determine whether the bacterium is transcribing the gene or not.
C It is a gene that produces a protein that fluoresces in response to the presence of the pathogenic toxin, allowing researchers to determine if the bacterium is in the mutualistic or pathogenic state.
D It is a gene that produces a protein that fluoresces in a way that allows researchers to easily determine whether the bacterium is in the mutualistic state or the pathogenic state.
E It is a gene that fluoresces in a way that allows researchers to easily determine whether the bacterium is in the mutualistic state or the pathogenic state.

Answer 3

D

Question 4

The introductory passage states that, “…some prokaryotes are also able to change their morphology or switch from benign to pathogenic forms by altering gene expression.” Does this help to determine whether enzyme activity or enzyme amount is changed during the pathogenic stage? Be careful to refer to what is meant by the statement in the passage rather than looking for any true answer.
Choose the best answer.
A Yes, because turning off gene expression conserves more energy and materials than inhibiting enzyme activity.
B Yes, because altering gene expression can influence whether enzyme inhibitors are produced and inhibitors influence enzyme activity.
C No, because altering gene expression does not affect the amount of enzyme present or the activity of the enzyme.
D Yes, because altering gene expression means altering transcription or translation to affect enzyme production (affecting the amount of enzyme produced).
E No, because altering gene expression does not affect the activity of the enzyme.

Answer 4

D

Question 5

Which of the following genetic elements is transcribed into a single mRNA?
A The operator
B The repressor
C The inducer
D The promoter
E The structural genes

Answer 5

E

Question 6

Which operons are always transcribed unless deactivated?
A Inducible operons
B Repressible operons
C Inducible and repressible operons

Answer 6

B

Question 7

Which operons are never transcribed unless activated?
A Inducible operons
B Repressible operons
C Inducible and repressible operons

Answer 7

A

Question 8

According to the animation, where on the DNA strand does a repressor bind?
A The inducer
B The promoter
C The structural genes
D The operator

Answer 8

D

Question 9

One way that regulation is often studied is by examining the effects of mutations. For example, mutations within the parts of the lac operon have been well studied. Which of these mutants would be considered a constitutive mutant?
A a mutation in the promoter for the operon
B a mutation in the gene for β-galactosidase
C a mutation in the gene for the repressor
D a mutation in the gene for β-galactosidase permease

Answer 9

C

Question 10

What would be the most likely effect of a mutation in the operator of a lac operon?
A β-galactosidase would not be produced.
B The repressor would not be produced.
C Regulation would occur normally.
D The genes would be constitutively expressed.

Answer 10

D

Question 11

Regulation by induction and repression are called negative control because __________.
A Transcription proceeds in the presence of the repressor protein.
B Translation proceeds in the presence of the repressor protein.
C Translation proceeds in the absence of the repressor protein.
D Transcription proceeds in the absence of the repressor protein.

Answer 11

D

Question 12

Define what an effector is in genetic regulation.
A Effectors are another name for the repressor protein that binds to DNA in negative control.
B Effectors are small molecules that only induce transcription of a specific gene.
C Effectors are small molecules that induce or repress transcription of a specific gene.
D Effectors are small molecules that only repress transcription of a specific gene.

Answer 12

C

Question 13

Which statement best explains why positively controlled genes have weak promoters and need an activator protein to help the RNA polymerase bind?
A The organism wants transcription to stop when the substrate (the activator protein) of the gene product is present.
B The organism only wants translation to occur when the substrate (the activator protein) of the gene product is present.
C The organism only wants translation to stop when the substrate (the activator protein) of the gene product is present.
D The organism wants transcription to occur only when the substrate (the activator protein) of the gene product is present.

Answer 13

D

Question 14

In certain circumstances, a single regulatory protein controls multiple operons. This situation would be called a(n) \_\_\_\_\_\_\_\_\_\_.
A regulon
B catabolite regulation
C multiple operon
D genetic regulation

Answer 14

A

Question 15

Which of the following examples describes a type of catabolite repression?
A Allolactose binds to a repressor, preventing it from binding to the operator of the lac operon.
B The presence of abundant tryptophan inhibits the Trp operon.
C When glucose is present, the lac operon is inhibited.
D A mutation in the operator of the lac operon prevents the expression of the genes needed for the bacterium to utilize lactose.

Answer 15

C

Question 16

One reason that regulation of gene expression is important is that it saves energy and materials from being used when they are not needed. At which point would regulation be most efficient in conserving energy and materials if the product of a gene is not needed?
A transcriptional regulation (regulation of whether transcription occurs)
B post-transcriptional regulation
C post-translational regulation
D regulation of translation

Answer 16

A

Question 17

Cells can regulate their metabolism by regulating enzyme activity or by regulating synthesis (i.e., by regulating whether they produce the enzyme for the reaction). Which of the following examples would be best when an enzyme needs to be available very rapidly?
A mRNA transcripts are produced but not translated until the enzyme is needed.
B An enzyme is activated by the binding of a molecule to its allosteric site.
C When the enzyme is needed, the relevant operon is repressed.
D When the enzyme is needed, the relevant operon is activated.

Answer 17

B

Question 18

Proteins required at approximately the same level throughout a cell’s growth cycle are often not subject to regulatory mechanisms and are constitutively synthesized.
A True
B False

Answer 18

A

Question 19

Hydrophobic interactions can be very important in determining protein shape. They are also important in interactions between DNA-binding proteins and DNA. Which of the following is an example of a hydrophobic interaction?
A Glutamine and tyrosine are attracted to glycine.
B Two cysteines form a disulfide bond.
C Alanine, glycine, and phenylalanine are positioned together.
D The nitrogenous bases of DNA are joined by hydrogen bonds.

Answer 19

C

Question 20

Van der Waals forces are important in sequence recognition by DNA-binding proteins. Which of the following examples is NOT an example of van der Waals interactions?
A A carbon atom shares electrons with four hydrogen atoms.
B Two molecules with permanent dipoles interact with each other.
C Two CCl4 molecules experience dispersion forces as a result of induced dipoles.
D A molecule with a permanent dipole is attracted to another molecule with an induced dipole.

Answer 20

A

Question 21

Transcriptional regulators bind most frequently at the \_\_\_\_\_\_\_\_ site of DNA.
A histone complex
B primary supercoil
C major groove
D minor groove

Answer 21

C

Question 22

How can DNA binding proteins (DBP) regulate transcription?
A DNA binding proteins can activate transcription.
B DNA-binding proteins can catalyze transcription.
C DNA-binding proteins can block transcription.
D All of the listed responses are correct.

Answer 22

D

Question 23

Some proteins that bind to DNA block transcription, whereas other proteins can activate transcription.
A True
B False

Answer 23

A

Question 24

DNA-binding proteins typically affect translation of a protein.
A True
B False

Answer 24

B

Question 25

When arginine is added to a culture growing exponentially in a medium without arginine, what occurs?
A All cellular growth ceases.
B Growth continues, but the production of enzymes required for the synthesis of arginine increases.
C Growth continues, but the production of enzymes required for the synthesis of arginine ceases.
D The cell returns to the lag stage of growth to synthesize the proteins necessary for the metabolism of arginine.

Answer 25

C

Question 26

Which type of regulator(s) specifically bind to operator regions of DNA?
A repressors and corepressors
B activators
C activators and inducers
D repressors

Answer 26

D

Question 27

Enzyme induction occurs
A when the organism is environmentally stressed.
B when the substrate is depleted.
C when the substrate is present.
D continuously.

Answer 27

C

Question 28

What occurs when an inducer is added to an environment containing an organism with a metabolic pathway controlled by a repressor?
A The inducer combines with the repressor and inactivates the pathway.
B The inducer combines with the substrate and blocks induction.
C The inducer combines with the repressor and activates the pathway.
D The inducer does not combine with, but functions as a chaperone molecule for, the enzyme-substrate complex.

Answer 28

A
BUT A IS FREAKIN WRONG!!!!
THE ACTUAL ANSWER, IS C. DUH.

Question 29

In negative control of transcription, how does the presence of an inducer affect transcription?
A The inducer prevents the repressor from binding to the operator.
B The inducer binds to the operator.
C The inducer causes the repressor to bind to the operator.
D The inducer does not bind to the operator.

Answer 29

A

Question 30

for transcription to occur.
The lac operon is an example of \_\_\_\_\_\_\_\_ control in which the presence of an \_\_\_\_\_\_\_\_ is required for transcription to occur.
A negative / activator
B positive / inducer
C negative / inducer
D positive / activator

Answer 30

C

Question 31

Which of the following do NOT bind to the promoter sequence during regulation?
A activators, inducers, and repressors
B repressors
C inducers
D activators

Answer 31

A
activators: bind to regulatory domains or DNA binding proteins, not the actual promoter
inducers: bind to repressors
Repressors: bind to operators

Question 32

The promoters of positively controlled operons require activator proteins, because
A RNA polymerase easily recognizes the consensus sequence.
B the promoters have nucleotide sequences that bind RNA polymerase weakly, which are not close matches to the consensus sequence.
C they are required to inactivate the repressor proteins.
D they are needed to bind to the allosteric site of RNA polymerase.

Answer 32

B

Question 33

Which statement is TRUE of two separate regulators controlling one individual operon?
A Two regulators trying to control the same operon will likely result in only one being maintained after several generations.
B One regulator will bind to the operator region whereas the other will bind to the promoter region so they can co-occur and co-regulate the operon.
C One regulator will likely control the transcription of one section of the operon, whereas the other regulator will control the other component.
D The two regulators themselves must respond to different signals, which enables both to control the operon differently.

Answer 33

D

Question 34

Considering the catabolite repression mechanism, which observation would make you suspect it is occurring?
A RNA polymerase bound to biosynthetic promoter sequences
B relatively low intracellular cyclic AMP levels
C elevated levels of transcripts for maltose and sucrose catabolism
D CRP bound to promoter sites

Answer 34

B

Question 35

Cyclic AMP is synthesized from ATP by an enzyme called ________ which is involved in ________.
A cAMP receptor protein (CRP) synthase / catabolite repression
B adenylate cyclase / catabolite repression
C cAMP receptor protein (CRP) synthase / transcriptional activation
D adenylate cyclase / transcriptional activation

Answer 35

B

Question 36

The synthesis of -galactosidase is regulated by \_\_\_\_\_\_\_\_\_\_.
A catabolite repression
B repression
C induction
D induction and catabolite repression

Answer 36

D